Rachel will drop this after defeating her in the Cargo Room.

Find the Burst 1 upgrade for Handguns in Resident Evil: Revelations, located in Guest Room 4 during Episode 3/Scenario 2.

Location:

1. In Episode 3/Scenario 2, after obtaining the Helm key, unlock the door to Guest Room 4 in the Upper Cabins area.
2. This room is located in a hall with an elevator.
3. Scan below the bed to find the Burst 1 upgrade.